Electroless plating is a technique conventionally used for self-aligned growth of gate metal contacts on a seed metal layer using low resistivity copper (Cu). The process succeeds primarily because Cu does not oxidize in the electroless Cu plating bath. On the other hand, aluminum (Al) readily oxidizes in aqueous plating baths so an electroless plating process has not yet been developed for a seed metal layer comprising Al. Al has a moderately higher resistivity than Cu, but a relative cost advantage. It is desirable to form self-aligned contacts on the source and drain regions while avoiding the formation of additional metallization on metal gates.
Features, elements, and aspects of the invention that are referenced by the same numerals in different figures represent the same, equivalent, or similar features, elements, or aspects, in accordance with one or more embodiments.